The present invention is directed to the same subject as disclosed in U.S. Pat. No. 5,261,646, issued Nov. 16, 1993. As disclosed in the '646 patent, a major concern for winches occurs during the process of letting out the winch cable when under a load. The motors typically used for winding cable onto the drum are not sufficient to brake the cable drum. Thus, a supplemental braking mechanism is used. Such braking mechanisms are typically capable of securing the drum against unwinding but not for controlled unwinding. A situation might occur, for example, where a vehicle is being lowered down a steep hill. The braking mechanism has to allow unwinding of the cable drum but at a slowed pace as compared to free fall.
The '646 patent discloses a mechanism whereby a cam mechanism operates to apply braking force when the motor's drive shaft is non-rotating. The linkage between the drive shaft assembly and cam mechanism is such that the braking force is released by the drive shaft when rotated in either direction. With the drive shaft rotating to unwind the cable and with the cable under load, the brake is released until the forced unwinding by the load outruns the drive shaft rotation at which point the brake is re-applied. The drive shaft then catches up and again causes brake release and the process is repeated. The brake mechanism includes a dampening action that permits sharp starts and stops to create a somewhat steady but controlled braking that produces the effect of a constant unwinding at the rate of the rotating drive shaft.
The '646 patent has common ownership with the present invention. The '646 patent, including the full disclosure of the drawings, description and claims, is incorporated herein by reference.